1. Field of the Invention
The present invention is directed to a method and apparatus for optimizing a work distribution, and in particular, to the optimization of work distribution along an assembly line or in a production process. This invention is applied, e.g., to assembling a wire harness, or a subassembly (hereinafter referred to as wire assembly) which forms a wire harness.
2. Discussion of Background and Other Information
Industrial products are generally manufactured using complex and multiple handling procedures. When large products, having a number of components, such as, for example, wire harnesses, are manufactured, more work space and additional workers may be involved.
A wire harness is an electrical network of, for example, a car, and may be considered to be equivalent to the nervous system of a human body. The wire harness has a plurality of branches derived from junction points on a main line (or sometimes from another branch line). Each wire that makes a connection from one branch to another branch has a crimped terminal that is inserted into an associated connector.
The assembly line for manufacturing a wire harness is based upon a preestablished standard time for manufacturing the product. However, when the number of operators (workers) or their positions at each station of the assembly line changes, the actual assembly time required to manufacture the wire harness changes from the preestablished standard time. This usually happens when new or less skilled workers are positioned at work stations that require a high degree of skill.
The process of assembling a wire harness may include a manufacturing process, an arranging process, a selecting process, and a gross-assembly process. For example, the wire harness manufacturing process begins by making one or more sub-assemblies (e.g., the manufacturing process). Each sub-assembly comprises some connectors and wires with crimped terminals on each extremity. The sub-assembly is then laid upon an assembly table (e.g., the arranging process), where a junction position is determined through the use of appropriate jigs (e.g., the selecting process) for additional wiring. When all the wiring is finished, the main line and the branch lines are bundled with, for example, vinyl tape, tubing, or other sheathing material (e.g., the gross-assembly process).
Most of these respective processes are performed by a flow production assembly line of approximately 10 to 20 workers. Some assembly processes may require significant manual assembly. In such manual assembly cases, the man-hours (assembling real man-hours) required to perform the work when a production variation occurs (or when one or more assembly workers are absent) greatly exceed a predetermined normal man-hours (preestablished standard man-hours) required to perform the work, resulting in delays and backlogs in the assembly process, and possibly affecting the quality of the completed product. Therefore, a conventional assembly line employs a manager who controls the work flow of the assembly line. The manager carries out the work distribution (work flow) based upon his experience and intuition by judging the length of experience and work capabilities of each worker in the assembly line.
The work distribution in the above-discussed assembly line frequently calls for the manager to consider the skill level of each worker, whether any workers are absent, the difficulty level of the work to be performed by the individual workers, and the difficulty in quantifying the same. As a result, it is often difficult to maximize the worker efficiency or to optimize the handling distribution.
In addition, when manufacturing comparatively large size products, such as, for example, a wire assembly, it becomes even more difficult to optimize the assembly procedure, due to the need to assemble or arrange components according to a work order determined in a preferential order on a drawing board (work bench) with a size of approximately 0.8 m by 4 m.